Fix feed validation output

tests/test_job_runner.py

@@ -0,0 +1,37 @@
+from pathlib import Path
+
+import pytest
+
+from repub.config import FeedConfig
+from repub.job_runner import _build_crawl_settings
+
+
+def test_build_crawl_settings_passes_feed_url_to_spider(tmp_path: Path) -> None:
+    settings = _build_crawl_settings(
+        out_dir=tmp_path / "out",
+        feed=FeedConfig(
+            name="Demo Feed",
+            slug="demo",
+            url="https://source.example/feed.rss",
+        ),
+        stats_path=tmp_path / "stats.jsonl",
+        feed_url="https://mirror.example",
+    )
+
+    assert settings["REPUBLISHER_FEED_URL"] == "https://mirror.example"
+
+
+def test_build_crawl_settings_requires_non_empty_feed_url(
+    tmp_path: Path,
+) -> None:
+    with pytest.raises(ValueError, match="feed_url setting is required"):
+        _build_crawl_settings(
+            out_dir=tmp_path / "out",
+            feed=FeedConfig(
+                name="Demo Feed",
+                slug="demo",
+                url="https://source.example/feed.rss",
+            ),
+            stats_path=tmp_path / "stats.jsonl",
+            feed_url="",
+        )